package likouJava;

public class 接雨水 {
    public int trap(int[] height) {
        int n = height.length;
        if(n == 0){
            return 0;
        }
        int[] leftMax = new int[n];
        leftMax[0] = height[0];
        for (int i = 1; i < n; i++) {
           leftMax[i] = Math.max(leftMax[i-1],height[i]);
        }
        int[] rightMax = new int[n];
        rightMax[n-1] = height[n-1];
        for (int i = n - 2; i >= 0 ; i--) {
            rightMax[i] = Math.max(rightMax[i+1],height[i]);
        }
        int ans = 0;
        for (int i = 0; i < n; i++) {
            ans += Math.min(rightMax[i] ,leftMax[i]) - height[i];
        }
        return ans;
    }

}
